1. Field of the Invention
This invention relates in general to certain new and useful improvements in a means and method for reducing power consumption of one or more lamps in a circuit arrangement and correspondingly reducing lumen output to a uniform lumen output level, while maintaining efficiency of operation of the lamps and the power source connected to the lamps for operation of the lamps, and more particularly to a means and method of the type stated which utilizes a load limiting control means for insertion in a series connection with respect to a lamp and the source of power thereof.
2. Brief Description of the Prior Art
In many cases, conventional fluorescent light fixtures are constructed so as to physically retain and energize a pair of phosphor excitable lamps, such as the fluorescent lamps. The ballast and circuitry in these fixtures are typically designed so that two lamps in a two-lamp fixture, for example, are essentially electrically 180 degrees out of phase. This arrangement is used in order to cancel out visible flicker to some extent. Thus, two lights in a fixture or otherwise lights in pairs are employed to reduce the noticeable effects of flicker, even though the extra lumen output of the two lamps are not necessarily required.
In many cases, it has been found in office buildings and other commercial installations, that it is possible to eliminate one or more lamps of the fixture without appreciably reducing total light output so that inefficiency and eye fatigue do not result. In other words, many commercially available fixtures were constructed so that an excess of light was generated for a given purpose.
In recent years, and due at least in part to severe shortages in available energy, and particularly electrical energy, and also due to the high cost of electrical energy, there has been an interest in reducing the available light output in order to reduce the total cost of operation. However, in many of the commercially available fluorescent lamp fixtures, the removal of one of the lamps, particularly in a series connected circuit of the lamps resulted in a very substantial inefficiency of operation. If the remaining lamp was able to operate at all, depending upon the circuit configuration, then there was a resultant inefficiency in that the remaining lamp produced less light output for a given level of power consumption, or otherwise, the ballast in the electrical circuit which operates the lamp operated inefficiently thereby decreasing operating life.
In order to obviate these problems, there has been an introduction in the market place of the so-called "phantom tube". The phantom tube is essentially a bulb or tube similar to that of the fluorescent lamp or similar phosphor excitable lamp which was removed and which is capable of being connected between the terminals in a fluorescent lamp fixture. In this way, when one of the operating lamps was removed, the phantom tube was inserted and the remaining lamp could operate with a reasonable degree of efficiency. These phantom tubes, in one embodiment, employ a capacitor connected between the sockets from which a lamp was removed, such as the type described in U.S. Pat. No. 3,956,665 to Westphal. In other cases, the phantom tube relied upon a nonreactive lamp circuit, as for example, as described in U.S. Pat. No. 4,053,811 to Abernathy.
In each case, the phantom tube while effective in permitting reduction in power, was oftentimes undesirable due to the fact that it drew attention to the fact that one of the operating lamps was removed. Thus, it always appeared as though one of the lamps in a two lamp fixture was burned out and not replaced. In addition, the removal of one or more of the lumen producing lamps oftentimes created uneven light distribution and was therefore ineffective for the desired purpose. In addition to the above, unless the capacitor or the power factor compensating element was not accurately established for a particular circuit, there was a resultant power factor loss.
In addition to the foregoing, the lamp substitute devices e.g. the so-called phantom tube, was ineffective, in some cases, due to the fact that it was not easy or convenient to repair the phantom tube, particularly in the event of a capacitor burn-out. Moreover, inasmuch as these tubes were constructed primarily of glass or lightweight plastic material, they had to be carefully packaged in order to reduce the incident of breakage or damage during shipment and transportation. This resulted in an increase in the cost of the shipment and hence the cost of the phantom tubes. Notwithstanding, even with careful packaging, there was also a substantial rate of breakage and damage as a result of shipment and for that matter, improper handling during storage.
There has been at least one attempt to reduce power consumption and also lumen output in a circuit configuration which employed two or more fluorescent lamps. This one proposal has been taught in U.S. Pat. No. 4,135,115 to Abernathy et al. However, in the Abernathy et al Patent, the device which is utilized is rather complex and includes a step-up transformer, as well as a plurality of capacitors and a resistive element. This device is constructed so as to at least step-up the voltage for a short period of time in order to achieve starting of the lamp. Moreover, this particular device is only effective for use with the so-called "rapid-start" circuit and is not effective for use in other circuit configurations, as for example, the so-called "instant-start" circuit, etc.
In addition to the above, the device in the Abernathy, et al Patent is also relatively ineffective in that it must be physically connected in the circuit by disconnecting one or more of the electrical lines with respect to the ballast. Thus, it was necessary to employ someone skilled in electrical circuit work, such as a licensed electrician to disconnect the power, break one or more of the lines and connect the device taught in the Abernathy et al Patent into the circuit arrangement. This resulted in down time, a substantial increase in installation costs and further, a very substantial increase in cost of the device itself.
The present invention obviates these and other problems in the provision of the very simple load limiting control means which is cable of being inserted in the circuit without the necessary disconnection of any of the electrical lines. Moreover, the device of the present invention is quite simple in its construction and permits a reduction of lumen output with a corresponding reduction of power consumption and which is highly efficient.